1. Field of the Invention
This invention relates to a method and mechanism for securing a two-way digital communication against eavesdropping. The applications of particular concern are financial transactions and Internet communications.
2. Description of the Related Art
With the advent of CMOS technology, and the rising financial losses due to credit-card fraud, it was natural for financial institutions to embed digital technology into credit cards and promote what is now known as the "Smart Card". The smart card was developed as an alternative to the traditional magnetic stripe technology, which proved to be vulnerable to snooping and duplication by professional hackers.
Regrettably, the smart cards presently being introduced in the market are based on a 17-year old technology which was first introduced by Rivest, Shamir and Adleman of RSA Corporation (U.S. Pat. No. 4,405,829). While capable of achieving a solid level of security in two-way digital communications, such a technology has the serious deficiency of depending on complex mathematical operations, such as multiplication, exponentiation, and modulo arithmetic. Consequently, most smart cards implement such two-way communication by incorporating on the card an advanced microprocessor, coprocessor, and large amounts of RAM and ROM. Not only such complexity raises the cost of the smart card, but it is further very difficult to embed such complex hardware into a thin, portable package, which must also be rugged to stand mechanical abuse.
The present invention introduces a new method for asymmetric encryption which does not depend on a pair of keys that must be calculated according to a mathematical formula. Rather, the method can use any arbitrary digital message as a test signal. A secret key recorded on an inaccessible ROM in the receiver encrypts the test signal and returns an encrypted message. However, such encryption is done according to a technique which makes it absolutely impossible to decrypt the message in any manner whatsoever and recover the secret key. Moreover, the circuitry required for performing such encryption is fairly simple and does not perform mathematical operations. Accordingly, the invention offers a simple hardware package that can be cheaply and reliably embedded into plastic cards, without a sacrifice in the level of security desired in digital communications.
Other aspects and features of the invention will be more fully apparent from the ensuing disclosure and appended claims.